1. Field of the Invention
The present invention relates to a process for producing a resin molded article having a hollow space inside, the resin molded article, hereinafter, being referred to as a "hollow molded article".
2. Description of the Related Art
Japanese unexamined patent publication Nos. Hei 4-212822 and Hei 7-144336 disclose a process for producing a hollow molded article utilizing an injection molding method having a core retracting system. In this process, a molten resin is injected with a high pressure into a cavity which is completely closed with a predetermined clearance. After filling the cavity with the resin, a movable core is retracted to expand the cavity while injecting a high-pressured gas into the molten resin. Consequently, a hollow space is formed in a resin substrate. However, such a method has been problematic in that a sink mark and a blister have been caused in a part of the hollow molded article in the vicinity of the hollow space and the appearance of the hollow molded article has been deteriorated because of the difference in a cooling speed of the resin and in a pressure applied to the resin between a part near to the hollow space and apart far from the hollow space. Additionally, there has been another problem that when molding of the hollow molded article and laminating of a skin material, such as one having a cushion layer and one having hair such as a carpet, onto a surface of the hollow molded article are carried out simultaneously, the cushion layer is crushed and the hair is laid in different degrees between the part near to the hollow space and the part far from the hollow space and the appearance of the hollow molded article is deteriorated.